In open-heart surgery, a blood pump for pumping blood is used to maintain the blood circulation. A known blood pump includes a casing, an impeller rotatably arranged in the casing, and a driving mechanism causing the impeller to rotate, and causes the impeller to rotate by the driving mechanism to take blood into a channel inside the casing and pump the blood outside the casing.
In this type of blood pump, for example, a rotating shaft for the impeller penetrates the wall of the casing and projects from the casing, and a driving motor is connected to the rotating shaft. In an area where the rotating shaft penetrates the wall of the casing, an axial sealing structure is provided to prevent leakage of blood. However, because the axial sealing structure is in contact with the casing and the rotating shaft, red blood cells and other components in the blood may be damaged at these points of contact to cause hemolysis, and stagnant blood flow at the points of contact may cause a blood clot. In addition, an issue may arise with durability of the sealing.
To address the foregoing, a blood pump supporting an impeller in a casing in a noncontact manner has been known. Such a blood pump includes a driving mechanism that causes the impeller to rotate by interaction between a magnet provided to the impeller and another magnet arranged outside the casing and driven for rotation by a driving motor. In a narrow gap between the outer peripheral surface of the impeller and the inner peripheral surface of the casing, a dynamic bearing is provided that supports the impeller in the radial direction with the pressure of the blood pumped in through rotation of the impeller. Furthermore, a controllable magnetic bearing is provided that supports the impeller in the axis direction by placing a bearing magnet provided to the impeller and a magnet core provided to the casing face to face with each other in the radial direction and controlling the magnetic force of the magnetic core depending on the position of the impeller (see Patent Document 1, for example).
[Patent Document 1] Japanese Patent Application Laid-open No. 2006-226390